Today in 1970, US Patent 3501934 A was issued, an invention of Albert W. Engel and Gerald J. Forbes, for their “Apparatus For Repairing Kegs.” There’s no Abstract, but the description states that the invention relates to a “method and apparatus for repairing metal kegs, such as the aluminum kegs used for containing beer. The apparatus includes a die shaped to the outside form of the keg. The deformed externally projecting parts of the keg are pressed into an area defining original confines of the keg. In other words all external projections are forced inwardly by pressure. To return the keg to its original condition, the keg is filled with water, and an explosive is placed in the keg. The explosive is detonated to blow the keg back to its original form. The method comprises a hydraulic means of expanding kegs against a closed die to return the kegs to their original shape.”
Reminds me of how SEALAB was formed in SF Bay. Check it out